A writing instrument making use of liquid ink contained in a reservoir and having a transfer rod is described, in particular, in document EP 0 516 538. The body of the instrument includes an internal partition which defines the reservoir for liquid ink in the rear portion of the body. The rear end of the transfer rod penetrates into the reservoir via said internal partition.
Such a writing instrument loses priming when the transfer rod is no longer fed with ink while the reservoir still contains liquid ink. This means that it ceases to write, which is naturally inconvenient for the user, particularly since the user may believe that the instrument needs to be discarded although it still contains usable ink.
On considering the description and the drawings illustrating embodiments of such a writing instrument in document EP 0 516 538, it will be understood that such loss of priming can occur when the instrument is used while its rod is not immersed in the ink, once a certain quantity of ink has already been used up. Given that the rear end of the transfer rod penetrates only a short way into the reservoir, the ink remaining in the bottom of the reservoir no longer reaches said rear end when the instrument has its tip pointing upwards. Once all the ink contained in the transfer rod has been used up, then priming is lost.
The same phenomenon can also be observed when writing with the tip pointing downwards, but with the instrument held at an angle and when only a small amount of ink remains in the reservoir.